Method of inhibiting plant growth



United States Patent f() Q v3,390,977 i METHOD OF INHIBITING PLANT GROW'I H John K. Leas'ure, 'Carbondale, Ill., and Dorsey R. Mussel],

Clare, Mich-I assi'g'n'ors to The Dow *ChemicaICompany, Midland, Mich, a'corporation of Delaware N Drawing. Filed'May' 11, 1966, Ser. No. 549,186 1 e. 5 Claims; (Cl. 71-79) directed to compositions and methods for the suppression and control of the growth of germinant seeds, emerging seedlings-and established plants of many undesirable weed species, and for defoliating plants and promoting the maturing ofcrops and facilitating their harvest.

According to the present invention, it has been discovered that the growth characteristics of-many plants may be modified or altered by contacting plants or' plant parts to the action of a growth-altering amount of a silane compound corresponding to the formulai In this and succeeding formulae, each G independently represents chloro or fluoro. More particularly, it has been discovered that the growth ofgerminant seeds, seedlings and established vegetation may be suppressed, defoliated, or'inhibited by exposing the seedsl'seedlinggroots or above-ground portions of growing plants to the action of a growth-altering or growth-inhibiting amount of the silane-compounds. It has been discovered further that with proper control of the dosage of the silane compounds, the maturation of many crop plants may be facilitated and their harvest promoted without substantial injury to that portion of'the plant to be harvested. Moreover, it has been found that the compounds have a substantial degree of selective toxicity for many undesirable broad leaf and narrow leaf plants. They are adapted to be employed for the selective control of broad leaf plants in stands of narrow leaf crop plants.

The silane compounds are liquid materials which are somewhat soluble in many organic solvents and of very low solubility in water. 7 k v The contacting of a viable form of plant, or of plant parts, to the action of the silane compounds gives rise to varying responses depending'upon the nature of the plant or plant part, the stage of growth or maturity of the plant, the silane compound employed and the dosage of silane compound at which the exposure is carried out. When large dosages are dispersed in growth media, a persistent inhibition of the growth of the seeds, emerging seedlings and established plants of many plant species is obtained. The weathering action of the sun, rainand possibly the decomposition of the silane compounds by theaction of bacteria, eventually reduces their concentration in the growth mediai Where plant maturation is concerned, the silane com- 3,390,977 r te eqq u 1??? poundsvare applied to the foliageof crops at altimeneaif the end of their normal growing season andat a do' sage sufii cie'nt to accelerate' the maturing of the 'ro'pfl h is treatment accomplishes an early and uniform. ripening of the fruit or other agricultural product and ,afretiid def folia'tion of the plant .so a s tol facilitate the harves the crop. In certain instances, as, with rice and. milo, the treatment results in a decrease in the moisture' content of the grain. Such a treatment permits an early harvest ofthe graincrop. p

The exposure of the plant-to the action. of a growth; altering amount of the silane isessential for the practice of'the present invention. The exact dosage to he e nployedto obtain such exposure is dependent upon'sucli facto'rsas soil type, depth to which the compounds are distributed in thesoil, rainfall, aswellas v plant:species to be controlled-and stage of gro'vvth thereofl In non;

selective herbicide applications, good results'are obtained when the germinant seeds or established plant's arelex; posed to dosages of from 10 to 50 pounds or more of the silane compounds per acre. In soil, good results are obtained when the compounds are distributed therein in amounts of from 0.5 to 100 parts or. more by weight per million parts by weight of soil. In selective applications forthe controlof the growth of broad leaf plants in narrow leaf crop plantings, a dosage of from 0.25 tov 10 pounds of the silane compounds per acre is desired.

Where plant maturation is concerned, good results are obtained at dosages of from 0.1 to, 10 pounds of the silane compounds per acre.

The method of the present invention may be carried out by applying to the above-ground portion of plants or by applying to the growth media the unmodified silane compounds. However, the present method also embraces the employment of a liquid or dust composition contain- 7 ing said compounds. In such usage, the compoundsmay be modified withone or more of a plurality of additaments or herbicide .adjuvants such as water, petroleum distillates, .or other organic solvent carriers, surface active dispersing agents and finely divided inert solids. Depending upon the concentration of the toxicant, such augmerited compositions are adapted to be distributed inor on the soil 'or on the above-ground portion of the plants or employed.v as concentrates and subsequently diluted withadditional inert carrier to produce the ultimate treating compositions.

' The exact concentration of silane compounds to be employed in compositions for the treatment of growth media and plants is not critical and may vary considerably pro: vided the required dosage of active agent is supplied in a the growth media or upon the above-ground surfaces of centration of toxicant may be from 0.5 to 50 percent by weight, although concentrations as low as 0.1 percent are sometimes employed. In compositions to be employed as concentrates, the toxicant oftentimes is present in a concentration of from about 1 to 98 percent by weight.

The quantity of treating composition to be applied may vary considerably provided the required dosage of active ingredient is applied in sufficient of the finished composition adequatelyrto cover the vegetation to be treated or to facilitate the penetration and distribution of the active ingredient in growth media. The required amount of active ingredient in the soil conveniently may be supplied per acre treated in from 40 to 27,000 gallons or more of the aqueous carrier, in 5 to 50 gallons of organic.solvent or in from 50 to 2,000 pounds of inert solid carrier.

i In the treatment of seedling weeds, good coverage is obtairied when using from to 100 gallons or more of finished spray composition per acrexWhere large succulent vegetation is concerned, it is frequently desirable to employ up to 250 gallons or more of the finished spray composition .per acre'to assure complete coverage of the above-ground portion-of the vegetation. In the application of dusts to plant foliage, goodresults are obtained with'fro'm 50 to 2,000 pounds of finished dust composition per acre, the only requirements being that the required toxicant dosage be supplied in sufficient dust to achieve good coverage of the foliage.

Liquidcompositions containing the desired amount of the silane compounds may be prepared by dissolving the toxicants in an organic liquid such as acetone, xylene or petroleum distillates or by dispersing the toxicants in water with or without the aid of a suitable surface active dispersing agent such as an ionic or non-ionic emulsifying agent. -T he aqueous compositions may contain one or more water-immiscible solvents for the silane compounds. In such compositions, the carrier comprises an aqueous emulsion, that is, a'mixture of water-immiscible solvent, emuls'ifying agent and water. The choice of dispersing and emulsifying agent and the amount thereof employed is dictated by the nature of the composition type and by the ability of the agent to facilitate the dispersion of the compound in the carrier to produce the desired composition. Dispersing and emulsifying agents which may be employed in the compositions include the condensation products of alkylene oxides with phenols and organic acids, alkyl aryl sulfonate, polyoxyethylene derivatives of sorbitan esters, complex ether alcohols, mahogany soaps and the like. The surface active dispersing agents are generally employed in the liquid compositions in the amount of from 1 to 20 percent by weight of the combined weight of the silane compound and the surface active agent.

In the preparation of dust compositions, the silane compounds are dispersed in and on a finely divided inert solid such as talc, chalk, gypsum and the like. In such operations, the carrier is mechanically ground with the compounds or wet with a volatile organic solvent solution thereof.

Similarly, dust compositions containing the compound may be prepared from various of the solid surface active dispersing agents such as bentonite, fullers earth, attapulgite and other clays. Depending upon the proportions of ingredients, these dust compositions may be employed as concentrates and subsequently diluted with additional solid surface active dispersing agent or with talc, chalk, gypsum and the like to obtain the desired amount of active ingredient in a composition adapted to be employed for the control of the growth of vegetation. Also, such concentrate dust compositions may be dispersed in water with or without the aid of a dispersing agent to form spray mixtures.

When operating in accordance with the present invention, growth-inhibiting amounts of the compounds or a composition containing the compounds are dispersed in any convenient fashion in soil or other growth media, i.e., by simple mixing with the growth media, by applying to the surface of soil and thereafter dragging or disking into the soil to the desired depth, or by employing a liquid carrier to accomplish the penetration and impregnation. The application of the spray and dust compositions to the surface of soil or to the above-ground surfaces of plants may be carried out by conventional methods, for example, with power clusters, boom or hand sprayers and spray dusters.

In a further method, the distribution in soil may be accomplished by introducing the toxicant in the water employed to irrigate the soil. In such procedure, the amount of water may be varied in accordance with the porosity and water-holding capacity of the soil in order to obtain the desired depth of distribution of the toxicant.

The following examples illustrate the present invention but are not to be construed as limiting.

4, EXAMPLE 1 Four parts by weight of one of the silane compounds, 0.08 part by weight of sorbitan trioleate (Span and 0.02 part of a sorbitan monolaurate polyoxyethylene derivative (Tween 80) were dispersed in 40 milliliters of acetone to produce a concentrate composition inthe form of a water-dispersible liquid containing one of the silane compounds as the active agent. From other silane compounds of the present invention, other such compositions were similarly prepared. Portions of these concentrate compositions were dispersed in water to produce aqueous spray compositions containing, respectively, 4000 parts and 10,000 parts by weightof one of the silanecompounds per million parts by weight of ultimate mixture. These compositions were applied to the foliage of plots of various plant species which were about 4 inches tall. The treatments were carried out with conventional spraying equipment, the plants being sprayed to the point of run off. Similar plots of the various plant species were left untreated to serve as checks. After about 2 weeks, the plots were examined to ascertain what control of the growth of the plants had been obtained. Compounds and plant species employed, together with results obtained, are set forth in the following table:

TABLE I Percent Kill of Population of Plant Sprayed Once to Run-off Test Compound 4,000 parts per 10,000 parts per million million Corn Tomato Japanese Beans m1 et Chloromethyl-dichlorometh ylsilane 40 30 100 Chloromethyl-difiuo methylsilane 20 50 100 EXAMPLE 2 TAB LE II Plant Species Percent of Entire Population killed 50 lbs. toxieant per acre treated Test Compound 20 lbs. toxicant per acre treated Japanese Radish Japanese Beans millet millet Chloromethyl-dichloromethylsilane 90 40 98 100 Chloromethyl-difiuoromethylsilane 100 100 100 100 Other compounds of the present invention, similarly tested, give similar test results, differing in species selectivity by individual compound tested.

EXAMPLE 3 One quarter of a pound of an :alkylated aryl polyether alcohol (Triton X':l00) is added with stirring to an aqueous dispersion containing 1 pound of chloromethylchloro-fluoromethylsilane mixture to produce an aqueous spray composition.

Twenty five parts by weight of chloromethyldichloromethylsilane are mixed with 65 parts of xylene and 10 parts of Triton X-100 to prepare a liquid ernu'lsifiable concentrate composition containing the silane compound.

In a similar manner, 90 parts by weight chloromethyldifl-uoromethylsilane are mixed with parts of a sor-bitan monolaurate polyoxyethylene derivative (Tween 80) to produce a concentrate composition in the form of a waterdispersi'ble liquid containing one of the silane compounds.

These concentrate compositions are dispersed in water to prepare aqueous compositions which have very desirable wetting and penetrating properties. The latter aqueous compositions and the aqueous spray compositions as above prepared are adapted to be employed to distribute the silane compounds in the soil or upon the foliage of plants in growth-altering amounts.

The compounds of the present invention are adapted to be employed in combination or in conjunction with other herbicidal or defoliant substances to attain the results of the combined application.

The chloromethyl-dihalo-methylsilanes of the present invention are known compounds, readily prepared by known methods. For example, chloromethyl-difluoromethylsilane is prepared by adding ch'loromethyl-dichloromethylsilane slowly to a stirred solution of 50 percent hydrofluoric acid in a polyolefin reaction vessel, releasing hydrogen chloride and fluorosil-ane as products of reaction. These are caught in -a Dry Ice cooled trap, the trap there-after permitted to warm very slowly to room temperature whereby to evaporate and remove most of the hydrogen chloride. The residue is thereafter distilled to obtain the desired chloromethyl-difluoromethylsilane, boiling at 64 C. at 744 mm. mercury pressure, absolute.

What is claimed is:

1. A method which comprises contacting living plant parts with a growth-inhibiting amount of a sil-ane compound of the formula:

wherein each G independently represents chloro or fl-uoro. 2. A method which comprises contacting living plant parts with a growth-inhibiting amount of a silane compound of the formula:

H r ol-rh-sr-orn References Cited UNITED STATES PATENTS 2,923,095 2/1960 Magimel-Pelonnier et al.

47-58 3,151,969 10/1964 'Stevens 71-2.3 3,183,076 5/1965 Leas-ure et al 712.7

JAMES O. THOMAS, JR., Primary Examiner. 

